That's interesting. You have posted that after Solus boots up you can read the USB stick. So that means the USB stick and the USB port are okay. But apparently bios can't read the USB stick. I wonder if the type of format of your USB stick is the problem? Maybe a bios that old can only read a fat32 format.
If you have the time and want to satisfy your curiosity about the problem you could try reformatting the USB stick as fat32 and then install Ventoy and an OS or two. Then try it and see what happens.
That's just my wild guess as to what might be going on. So don't take it too seriously.
